In order to maintain furnaces in proper operating condition for preparing molten metal for casting operations, the refractory insulative lining of the furnace must be replaced about every eight weeks. In order to replace the lining, the furnace must be shut down and allowed to cool, and the existing lining must be removed, exposing the structural walls of the furnace. Following removal of the worn lining, the replacement process has, in the past, generally included the steps of 1) lowering a lining form into the furnace to form a refractory lining of uniform thickness; 2) aligning the lining form within the furnace to provide a uniform space between the exterior of the lining form and the interior of the furnace; 3) wedging the lining form, after it has been aligned, to maintain it in the aligned position; 4) pouring the refractory lining material into the space between the lining form and the furnace wall; 5) holding the lining form motionless relative to the furnace wall while compacting the refractory material with a vibrator; and 6) gradually heating the lining form to harden the new refractory lining.
In the past, there have been no fixtures to assist in the accomplishment of steps 1-5 above, and the work was conducted manually by skilled workmen, and satisfactory completion was very time consuming and required great skill and attention. It is very important for reliable operation of the furnace that the lining form be accurately aligned with the furnace to obtain a uniform layer of refractory material at the furnace wall, and it is likewise important that the lining form be held motionless in its concentric alignment with the furnace while the refractory material is being compacted.
In the past, steps 1-3 were performed as follows:                a lining form was lowered into the furnace with an overhead crane;        a plumb-bob bar was placed over the lining form into two furnace alignment holes;        a worker had to climb down into the interior of the lining form, using a ladder, and take directional measurements of the space between the lining form and the furnace wall;        the crane operator had to use the directional measurements received from the worker to manipulate the overhead crane to locate the form in an assumed concentric position.        
The steps of measurement and relocation had to be repeated again and again until the lining form was positioned so that the space between the lining form and the interior furnace was uniform within one quarter of an inch.
Following the completion of steps 1-3, steps 4 and 5 were performed as follows                the lining form had to be wedged into the aligned position by workers without destroying the alignment;        when the lining form was wedged into position within the furnace, the overhead crane was used to pour particulate refractory material into the relatively narrow space between the lining form and the furnace wall;        after the space between the lining form and furnace was filled with the particulate refractory material, clamping bars were manually installed on top of the form in an attempt to hold the lining form motionless while the refractory material was being compacted with vibrators.        
Finally, the lining form was heated from within with a gas torch to harden the new lining and complete the process.
Because of the relatively narrow space between the lining form and the furnace wall, and the difficulty of accurately directing the particulate refractory material into the space, the pouring operation was restricted to the use of bags of refractory material that were no larger than 100-pound capacity.
This prior process was very time consuming and required the attention and care of skilled workmen for its successful completion.